Treatment of a patient with renal insufficiency is typically carried out according to a treatment plan created by a caregiver, such as a physician, based on certain therapeutic objectives or targets. The treatment plan may comprise a schedule of treatment sessions and specific control settings of the dialysis machine for each scheduled treatment session. The control settings are given for a number of machine-related parameters, such as duration, dialysis fluid composition, dialysis fluid flow rate, blood flow rate, type of dialyzer, etc. The control settings for each treatment session are normally strictly adhered to. The treatment plan typically also includes dietary advice, medications, frequency of blood samples for follow-up, etc.
The overall goal of the treatment plan is to achieve a desired patient status, viz. normalization of fluid balance and blood parameters of the patient. This may include normalization of fluid status, removal of uremic toxins, normalization of acid/base balance, and normalization of specific electrolytes, such as sodium, potassium, calcium, phosphate, etc. The caregiver designs the treatment plan based on clinical experience and knowledge about the specific patient. The outcome of the treatment plan may be followed by taking regular blood samples, e.g. monthly, allowing the treatment plan to be adjusted by the caregiver to better achieve the desired patient status.
This technique of determining the control settings of the dialysis machine and other aspects of the treatment plan presumes that each treatment session is scheduled according to the treatment plan and is carried out exactly with the prescribed control settings. In other words, it does not allow for any flexibility in when and how to carry out an individual treatment session. In the future, it may be foreseen that more renal replacement therapy will be carried out in the home of the patient, instead of in a clinic. In such a situation, the patient may desire to schedule the treatment sessions more according to his/her wishes and less according to a fixed schedule. It is not unlikely that increased demands for flexibility may arise also in clinical environments.
The current technique of determining the treatment plan requires involvement of the caregiver every time a change is to be made to the treatment plan. The required effort of the caregiver may also be significant, since the control settings need to be determined and re-evaluated manually, as the case may be.
Furthermore, since the treatment plan is determined empirically by the caregiver, it is not uncommon or unlikely that some patients underachieve the desired patient status and possibly develop adverse conditions.
There have been attempts in the prior art to mitigate these shortcomings.
US2010/0010424 discloses a peritoneal dialysis system that includes a number of modules which are designed to generate a number of default prescriptions to be downloaded into a dialysis machine. A prescription defines all control settings for the dialysis machine such as APD type, solution type, therapy time, and fill volume. A prescription optimization module is operated to automatically generate all possible regimens that fit within given ranges of therapy inputs, to achieve specified therapy targets for a specific patient. A filter module applies a filter that specifies the patient's preference and caregiver's performance requirement to narrow the number of regimens to a manageable few. The caregiver and patient then agree upon 3-5 regimens, which are downloaded as default prescriptions into the dialysis machine. For example, the default prescriptions may be a low UF (ultrafiltration) prescription, a standard UF prescription and a high UF prescription. At the onset of a treatment session, the machine may automatically select one of the default prescriptions, based on the patient's daily weight and possibly the patient's blood pressure. Alternatively, the machine may allow the user to choose from one or more default prescriptions.
Although this system offers increased flexibility in scheduling treatment sessions, the patient still has limited options and the treatment session may result in significant deviations from the desired patient status.
US2007/0175827 discloses a renal disease management system with a renal therapy device and an implanted cardiac rhythm management (CRM) device having sensors for measuring physiological parameters of the patient. The measured physiological parameters are transmitted to the renal therapy device which is configured to modify the renal therapy applied to the patient in response to the received parameters. Thus, the system includes feedback control that modifies the control settings of the renal therapy device during the course of a treatment session.
By the same token, EP1396274 discloses a blood treatment equipment capable of adjusting the duration of treatment session to achieve a prescribed dose target. The adjustment of duration is based on actual measurements of dialysance during treatment, and recalculation of remaining time. This system also reacts to measured changes during the course of a treatment session based on feedback control.
Neither of these systems provide any assistance for the caregiver or the patient in determining appropriate control settings for the treatment session.
The prior art also comprises WO93/00938 which discloses a control system for a dialysis unit. The control system is connected to sensors for monitoring parameter changes in plasma volume, total weight loss and total sodium removal. The control system allows the operator of the dialysis unit to enter changes in these parameters to be achieved during a treatment session, and the control system then computes appropriate machine parameters to be used by the dialysis unit. The control system is operable in an automatic control mode, in which the control system uses a mathematical model that describes the patient-dialysis unit system as an isolated system with the machine parameters as input and the changes as output. The control system is also operable in a manual mode, in which constant values of the machine parameters are calculated in a conventional way without the use of the mathematical model. Even if this system may assist the caregiver in determining control settings for a treatment session, it requires the caregiver to estimate, based on clinical experience and knowledge about the patient, the change to be achieved in each of the parameters measured by the sensors so as to attain a certain desired patient status after completion of the treatment session. This is not an easy task, and errors in the estimated changes may lead to significant deviations from the desired patient status, which ultimately may pose a risk to the patient's health.
US2004/0057037 and US2007/0135750 disclose control systems with feedback control that modifies control settings of a blood treatment device during the course of a treatment session. In US2004/0057037, the feedback control is operated to match an ideal curve for the rate of change in circulating blood volume, based on a continuous measurement of hematocrit values. In US2007/0135750, the feedback control is operated to withdraw a given amount of potassium, based on the output of a potassium-sensitive sensor in the dialysis fluid outlet line. These feedback control systems still confront the caregiver with the challenging task of estimating the changes to be achieved during the treatment, so as to attain a desired patient status.
DE102006032926 discloses a dialysis system which provides for manual input of duration and dose for a treatment session, whereupon the system calculates a desired clearance for the treatment session to achieve the dose. The desired clearance is shown to the caregiver who sets the dialysate fluid flow rate and the blood flow rate based on table data. In a variant, the dialysis system automatically determines one of the dialysate fluid flow rate and the blood flow rate, based on manual input of the other of the dialysate fluid flow rate and the blood flow rate. Although this system may offer increased flexibility in scheduling treatment sessions, the patient still has limited options since at least one of duration and clearance needs to be fixed. Furthermore, the treatment session is controlled with respect to dose (KT/V), which is a known measure of the effectiveness of a treatment, but has no causality with the physiological status of the patient after the treatment session. Thus, even if the caregiver empirically estimates a dose for the treatment session, the physiological status of the patient after the treatment session may deviate from the desired patient status.